The invention relates to an integral optical device composed of a photosensitive glass body having an optical pattern developed therein by a spatially varying property such as a refractive index change. The change is due to formation of colloidal metal particles and/or crystalline microphases nucleated by such particles. The pattern may be confined to one surface of the glass, as in the case of a grating pattern, or may be a lens system extending through the glass body, such as might be used for imaging purposes.
In one form of particular interest, the optical pattern is composed of at least one transparent lens system having a radial gradient refractive index distribution of prescribed nature. For present purposes, a lens system may be considered as a cylindrical zone extending through a glass body and terminating on opposite faces of the glass body in planar surfaces that function as lens-like elements.
U.S. Pat. No. 4,403,031 (Borrelli and Morse) discloses a method of producing an optical pattern in a porous glass by impregnating the glass with photolyzable organometallic material and selectively photolyzing the impregnated glass. Among the optical patterns that may be created are gradient refractive index patterns, such as lens systems, and optical density patterns.
Optical devices produced with impregnated porous glass show considerable promise, but a non-porous glass body would have obvious advantages in subsequent maintenance. While the porous glass may be consolidated to render it non-porous, that involves a high temperature treatment that is expensive and may result in pattern distortion or deterioration.
The possibility of creating a strip lens by grinding and polishing individual glass or plastic rods has been recognized. The individual rods are arranged in a pattern and bonded in a fixed relation. However, the extreme problems of production and alignment have also been recognized.
Accordingly, a currently commercial imaging device relies on optical effects generated by an array of minute surfaces, each having a defined gradient refractive index distribution. The array is produced by bundling a configuration of optical fibers wherein each fiber has a defined radial gradient index distribution imparted thereto, as by ion exchange or material impregnation.
This device involves a difficult alignment step which limits the device to a maximum of two linear arrays of lens. Further, while decrease in lens size would be desirable, this aggravates the bundling and aligning problems.